The present invention relates to a control system for a picture-display apparatus employing display devices such as, for example, liquid crystal display devices having a high display resolution rate.
Recently, a still picture conference apparatus (communication conference apparatus) has been proposed, which apparatus enables the holding of a tele-conference utilizing documents therein. Holding of such a tele-conference utilizing documents can not be enabled by a simple tele-conference apparatus. Instead, a complex apparatus, such as that of the conventional art, is needed. Such a complex still picture conference apparatus employs, in addition to a picture displaying function, the following functions for executing a tele-conference: a speech function, a facsimile function for transmission and/or receiving data of documents to be utilized in the conference, a tele-writing communication function for drawing pictures on a still picture displaying a document used in the conference, a still picture conference function for enabling the conference to proceed, and a document storing function for storing documents utilized in the conference. Such a still picture conference apparatus enables the holding of a conference in which documents to be utilized in the conference are transmitted and/or received as necessary, the transmission and/or receiving being executed among terminals used by respective members participating in the conference. Thus, in addition to utilizing the speech function or the tele-writing communication function, the members may refer to the transmitted and/or received documents in the conference.
A problem may occur in such a tele-conference using such a still picture conference apparatus in a case where a plurality of members (persons) in a common location (first location) participate in a conference which is held, for example, between the first location and another location (second location). In this case, the plurality of members in the first location commonly may use one terminal of the still picture conference apparatus in the conference, the plurality of members in the first location, for example, being present in a common room. Thus, the plurality of members in the first location have to be positioned to surround the terminal of the apparatus. Thus, some of the plurality of members in the first location can read contents of a picture displayed on the screen accompanying the terminal, because these members can hook at the front side of the screen. On the other hand, the remaining members in the first location can not read the displayed contents of the picture because they can not stand in front of the screen.
The above problem may be eliminated by providing a respective terminal with such a still picture conference apparatus for each member. Each member may the operate their own terminal independently from operations executed by the other members.
However, provision of such a plurality of terminals for such a still picture conference apparatus for one location as mentioned above may result in the cost of the conference becoming high. Further, such provision of a plurality of terminals for the still picture conference apparatus necessitates that a MCU (multi locations connection unit) function for connecting a plurality of still picture conference apparatus located in one location be provided, even when the conference is held between just two different locations. However provision of the MCU function may result in the cost of the conference becoming high.
To eliminate the above problem, the following method has been proposed. A plurality of picture displaying apparatus may be provided, each of the plurality of picture displaying apparatus having, from among the functions employed by the above mentioned still picture conference apparatus, only the picture displaying function. That is, each of the plurality of picture displaying apparatus does not employ the functions of the still picture conference apparatus other than the picture displaying function, such other functions including, for example, the facsimile function. One of the above picture displaying apparatus is given to each of the members (persons) present in a common room of a common location. Each of the given (slave) picture displaying apparatus displays the contents of a picture distributed from a master still picture conference apparatus provided for each location. Thus, the members who have been respectively given one of the slave picture displaying apparatus can see therewith the identical contents of the picture simultaneously, the identical contents of the picture being distributed from the master static conference apparatus.
However, use of a method such as one in which identical contents of a picture are distributed to each slave picture display apparatus as mentioned above results in the following problems.
A first problem is that the sizes of both such a master still picture conference apparatus and such a slave picture displaying apparatus become large. This problem occurs in a case where both the master still picture conference apparatus and the slave picture displaying apparatus employ a CRT (cathode ray tube) device as means for displaying the contents of a picture distributed from the master still picture conference apparatus to the slave picture displaying apparatus. This distribution of the displaying contents of a picture may be executed by obtaining a display signal (for example, an NTSC (National Television System Committee) composite signal) which is provided to a CRT device in the master still picture conference apparatus so that the displaying contents of a picture can be displayed. The obtained display signal is then distributed to the slave picture displaying apparatus, the distribution being executed by using a coaxial cable. Such constructions of the master still picture conference apparatus and the slave picture displaying apparatus result in the sizes thereof becoming large, as mentioned above. Thus, a large conference room will be required for such a large apparatus.
A second problem is the high cost of a signal transmission system for distributing of the displaying contents of a picture from the master still picture conference apparatus to the slave picture displaying apparatus. The reason why this system is expensive will now be explained. A picture displaying function, which will be described below, is preferably provided (by such a master still picture conference apparatus) for such a conference as using the master still picture conference apparatus. The CRT device in the master still picture conference apparatus may display a fine A4 size picture on the screen (a resolution rate of the displayed contents of a picture being high) comprising, for example, 1024 lines, each line comprising 1280 pixels. A displaying signal transferred with a very fast clock signal is needed so that such a high-resolution-rate of the displayed contents of a picture can be distributed from the master still picture conference apparatus to the slave picture displaying apparatus, the distribution being executed by using the displaying signal. Such a system employing such a displaying signal transferred with a very fast clock signal results in the cost of the signal transmission system becoming high.
If neither the master still picture conference apparatus nor the slave picture displaying apparatus employs a CRT device but instead employ a liquid crystal display device as means for displaying the contents of a picture, the above first problem may be eliminated and thus the sizes of these apparatus may be relatively small. However, even if the liquid crystal display device is employed as means for displaying the contents of a picture, the above second problem will not be overcome, that is, the costly signal transmission system has to be employed.